Projectile propulsive system with pressure-actuable arming means



p 1965 ABESCAT ETAL 3, ,8

PROJEGTILE PROPULSIVE SYSTEM WITH PRESSURE-ACTUABLE ARMING- MEANS FiledJuly 9, 1965 2 Sheets-Sheet 1 150mm HBESCAT 71400055 BLAND/N JZ-AN(iv/0r EM/L E 6 r4 UFF ra-WWW HTTORNE Y5 Sept. 14, 1965 ABESCAT ETAL3,205,321

PROJECTILE PROPULSIVE SYSTEM WITH PRESSURE-ACTUABLE Filed July 9, 1963ARMING MEANS 2 Sheets-Sheet 2 l/VVE/VTO/FS' A 50 04 0 4555047- Aca U655.4 4/1/0/A/ J54 00/4 407' fM/A 5 5 TAUFF mAVQm ATTORNEYS United StatesPatent 912,613 Claims. (Cl. 102-49) This invention relates to propulsivecharges for weapons having detonatable explosivecharges. It relatesparticularly to safety systems for use in connection with propulsivecharges for self-propelled military projectiles, such as rockets.

It is necessary for such self-propelled projectiles which carryexplosive Charges to include one or more internal safety devices toprevent the explosive charge from being detonated before the projectileis sufiiciently far from the launching station; damage to the personnelor equipment of the launching station or adjacent friendly areas is thusavoided if the projectile goes oif course or its detonation system isprematurely actuated. Projectiles may be fired from fixed groundstations or from moving vehicles, which may be near the military frontor some distance behind it, and an appropriate safety delay must beimposed in these various circumstances; in the case of a weapon firedfrom an aircraft, the charge hould be prevented from exploding until theprojectile is a safe distance from the aircraft, having regard to thecourse of flight of the aircraft under the particular operationalconditions.

It is an object of the invention to provide a simple safety device foruse in self-propelled projectiles having an explosive charge, adetonator for the explosive charge and a pressure-actuable device forarming the detonator. A propulsion unit for use in the combustionchambers of such a projectile compiises, according to the invention, acombustible propulsion charge, and at least one passage leading from apoint within the charge to a part of the projectile gastightly separatedfrom the combustion front and communicating with the pressure-actuabledevice, whereby combustion gases are enabled to pass to such device whenthe combustion front has reached the mouth of the passage.

Preferably more than one passage is provided; the passages should bearranged so that the advance of the combustion front is not affected,and they are thus preferably within thermally insulated tubes arrangedat the periphery of the combustion charge. The invention may be utilizedfor the arming after a predetermined delay of any pressure-actuabledevice, which may be situate in any convenient part of the projectilewhere it can be connected to the detonator. When the propulsive chargehas burnt down to reveal the end of the tube, the pressure of thecombustion gases is transmitted through the tube to the arming device.

One preferred embodiment of the invention will be described withreference to the accompanying drawing, in which;

FIG. 1 is a vertical section of a propulsion unit,

FIG. 2 is a cross-section along the line IIII of FIG. 1, and

FIG. 3 is a sectional view similar to FIG. 1 showing the explosivecharge and firing cap of the projectile and the detonator for strikingthe cap to explode a charge.

Referring to the drawings, the propulsive charge I is generallycylindrical in shape; one end In is flat and con- "ice stitutes thecombustion face, which is rearmost in flight. The charge is covered,except on its combustion face, by a thermally insulating and protectivelayer 2, which is shaped externally to fit a particular combustionchamber, and is illustrated with a forward end of spherical shape forthis purpose. Three small-bore copper tubes 3 debouch at the forward endof the charge, and their other ends 315 are all the same distance fromthe combustion face, and covered by the charge; these tubes are embeddedthroughout their length in the insulating layer 2, which is formed intoan additional layer 2a around them, so that the hot gases whichultimately pass down the tubes are prevented from igniting the adjacentcharge ahead of the normal combustion front.

In use, the propulsion unit is placed in the combustion chamber 6 (shownin broken lines) of a self-propelled projectile. A gasket 4 of syntheticplastic is arranged between the forward end of the charge and the closedend of the chamber, so that a cavity 7 is formed into which the ends 3aof the tubes debouch; this cavity is connected by an opening 5 to adevice for the arming of the detonator for the explosive charge. Suchdevice can be a piston maintained at rest by a calibrated spring, by arupturable pin or other element, or by any other mechanism which can bereleased by a known force, and it can operate by removing a shutter frombetween the detonator and explosive charge, by moving the detonatoritself, or by other known means. By way of example there has been shownin FIG. 3 a device for arming the detonator for the explosive charge. Astriker 8 carrying a firing pin 8a is held in an inactive position by abolt 9 which is itself held in fixed position by a metallic shear pin10. While a specific device has been illustrated for arming thedetonator for the explosive charge, the detonator may be armed by othermeans, such as those already mentioned.

When the charge is ignited at the face In, the combustion gases aregenerated and escape from the rear of the chamber, and the combustionfront advances, and until it reaches the plane in which the ends 312 ofthe tubes lie, the pressure in the cavity 7 is the same as thatprevailing before the combustion (i.e the ambient atmospheric pressure).When the combustion front reaches the mouth or end 36 of the tube, thecombustion gases pass down the tubes 3 and the pressure in the cavity 7rises until it is equal to that produced in the front of the chamber;the gases pass through the opening 5 to the arming device, e.g. thelower end of the bolt 9, and actuate it by their pressure. Under thisaction, the shear pin 10 is ruptured, the bolt 9 is displaced upwardlyunbolting the striker 8 which, upon impact of the projectile, will befree to move the deceleration due to shock, to strike the percussion capwith the firing pin 8a carried thereby and explode the explosive chargeof the projectile. The detonator is thus armed according to the methodchosen, adapted to the nature of the elements of the explosive charge.The arming circuit being gastight, the pressure rise is established withthe passage of a very small amount of cornbustion gases, so that heatingof the tubes and of the arming device is negligible.

The resistance of the shear pin 10 or other system opposing the movementof the bolt 9 is regulated so that the arming of the detonator is onlyachieved at a predetermined minimum pressure. Consequently, if thepropulsive charge does not become sufiiciently ignited to give adequatepropulsion, but smoulders slowly over a long period then, even thoughthe ends of the tubes may eventually be uncovered, there will not besufiicient gas pressure to actuate the mechanism for arming thedetonator. If the combustion is correctly initiated but ceasesprematurely, or the propulsion unit is prematurely ruptured before theend of the selected delay preiod, the ends of the tubes will not beuncovered and there will be no arming of the fuse. The arming of thedetonator only takes place if the propulsion system of the projectilehas functioned properly during the selected delay period and,consequently, when the projectile ha travelled the correspondingdistance, the delay being proportional to the thickness of the layer ofpropulsive charge to be burnt before the ends 3b of the tubes areuncovered.

The safety system according to the invention can be combined with othersystems based on other principles (e.g. autorotation or acceleration) sothat the safety of the projectile is ensured by two or more independentor interdependent series of safety systems.

The tubes need not be of copper, but may be of other metals, or ofsynthetic plastics material, or they may be simple orifices made in thecharge and provided with an inhibitory covering.

We claim:

1. A propulsion unit for use in the combustion chamber of aself-propelled projectile having an explosive charge, a detonator forsaid charge, a pressure-actuable device for arming the detonator, and acombustion chamber, in which the unit comprises a combustible propulsioncharge fitting into the combustion chamber, and at least one passagehaving a mouth disposed at a point within the chamber normally coveredby said charge leading to a part of the projectile gastightly separatedfrom the combustion front and communicating with the pressureactuabledevice, whereby combustion gases are enabled to pass to such device whenthe combustion front has reached the mouth of the passage.

2. A propulsion unit according to claim 1, in which the part of theprojectile separated from the combustion front is a forward portion ofthe combustion chamber.

3. A propulsion unit according to claim 2, which includes a thermallyinsulating and protective layer which encloses the propulsive chargeexcept on its ignition face, and in which the passage is constituted bya tube running along the periphery of the propulsion chamber andseparated from the propulsive charge by the insulating layer.

4. A propulsion unit according to claim 3, in which the tube is formedof metal.

5. A propulsion unit according to claim 3, in which the tube is formedof synthetic plastics material.

References Cited by the Examiner UNITED STATES PATENTS 695,57 8 3 /02McIntyre 102-49 2,145,507 1/39 Denoix 10249 2,918,870 12/59 Meister102-49 3,049,080 8/62 Schermuly 10234.4

BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL FEINBERG, Examiner.

1. A PROPULSION UNIT FOR USE IN THE COMBUSTION CHAMBER OF ASELF-PROPELLED PROJECTILE HAVING AN EXPLOSIVE CHARGE, A DETONATOR FORSAID CHARGE, A PRESSURE-ACTUABLE DEVICE FOR ARMING THE DETONATOR, AND ACOMBUSTION CHAMBER, IN WHICH THE UNIT COMPRISES A COMBUSTIBLE PROPULSIONCHARGE FITTING INTO THE COMNBUSTION CHAMBER, AND AT LEAST ONE PASSAGEHAVING A MOUTH DISPOSED AT A POINT WITHIN THE CHAMBER NORMALLY COVEREDBY SAID CHARGE LEADING TO A PART OF THE PROJECTILE GASTIGHTLY SEPARATEDFROM THE COMBUSTION FRONT AND COMMUNICATING WITH THE PRESSUREACTUABLEDEVICE, WHEREBY COMBUSTION GASES ARE ENAGLED TO PASS TO SUCH DEVICE WHENTHE COMBUSTION FRONT HAS REACHED THE MOUTH OF THE PASSAGE.